Abstract:
:The presence of two liquid-crystalline phases, alpha and beta, in mixed bilayers of dimyristoylphosphatidylcholine/cholesterol was detected by the changes in the distribution of the fluorescence lifetimes of t-PnA, as analyzed by the Maximum Entropy Method. The formation of the liquid-ordered beta-phase, in the 30-40 degrees C temperature range as a function of cholesterol concentration (0-40 mol%), could be related quantitatively to the relative amplitude of a long lifetime component of the probe (10-14 ns). Based on this evidence, the phase behavior of mixtures of the unsaturated lipid palmitoyloleoylphosphatidylcholine and cholesterol was determined using the same technique, for cholesterol concentrations in the 0-50 mol% range, between 10 and 40 degrees C. It was found that two liquid-crystalline phases are also formed in this system, with physical properties reminiscent of the alpha- and beta-phases formed with saturated lipids. However, in this case it was determined that, for temperatures in the physiological range, the alpha- and beta-phases coexist up to 40 mol% cholesterol. This finding may be of significant biological relevance, because it supports the long held notion that cholesterol is responsible for the lipid packing heterogeneity of several natural membranes rich in unsaturated lipid components.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Reyes Mateo C,Ulises Acuña A,Brochon JCdoi
10.1016/S0006-3495(95)80273-0subject
Has Abstractpub_date
1995-03-01 00:00:00pages
978-87issue
3eissn
0006-3495issn
1542-0086pii
S0006-3495(95)80273-0journal_volume
68pub_type
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